Skinny Dipping [OPEN]

I hate my sister, I hate my sister, Casey thought to herself. I'm absolutely insane and I hate my sister. She glanced back over her shoulder, where Lyssa was laughing and waving her on. Taking a deep breath, Casey turned back around. I'm a Gryffindor, I can do this.
It was currently about midnight, and like the insane children they were, Casey and Alyssa had decided to play Truth or Dare. And Casey's latest dare was skinny dipping in the Balck Lake. As in completely naked. In February.
I'm insane, she thought again, then began stripping in the cold air. At least this would be much different from that time she jumped into Lake Michigan in April. It couldn't be much colder than that.
When she was finally devoid of clothing, Casey took one more deep breath and plunged in. She gasped as the icy cold took her breath away, but quickly became used to it. She slid in and out of the water like a fish, enjoying the sensation she hadn't felt in a while.

Alyssa watched as her sister jumped into the water. She started laughing. They had been playing truth or dare, and this had been her genius dare. She just hoped she didnt get caught.

(OOC: I meant to write in the title, this is OPEN!)

Casey surfaced about 10 feet from land and shook her sleek, wet hair. "Come on in!" she called quietly. "The water's fine!" She grinned and flipped over, diving back downinto the depths. This wasn't part of the dare, but she was having too much fun now to stop.

((OOC- You can go back and edit the title))

Alyssa looked shocked at her sister. It was freezing out, how was she not cold. And then she dives back down.
Alyssa shivers as the wind wipps accross her small frame. Her PJ's and sweatshirt aren't all that protective. Alyssa watched as her sister splashed around in the cold water. Yeah, I'll keep my clothes on, she thought.

(OOC, Oops, didn't know that!)

Casey laughed at her sister's shivering, but did feel bad. "You're a witch Lyssa, just cast a warming charm on yourself!" she called, then went back to sliding through the water.
She had to swim for an agreed 10 minutes and felt she was getting close to the end of her time. She was about to call out to her sister to ask when she was interrupted by a shout from another person. She spun in the water to face them.

Alyssa cast a warming charm, feeling stupid for not thinking of it herself. Then sat down on the ground, she was counting down the time Casey had left, when she heard a shout. Looking around she located the person.
Oh, crap!, she thought.